Infectious Abortion 475 



serious in the cow, but it is questionable if this is correct in all 

 respects. The loss from single abortion is generally greater in 

 the mare than in the cow. A large proportion of calves are 

 destroyed at once or soon after birth because they are virtually 

 worthless or their raising entails more expense than their ulti- 

 mate value when grown. The principal loss in the cow is the 

 interference with the milk yield, which is of course highly im- 

 portant. In the case of the brood mare, it is desired to raise 

 each foal and its death becomes a serious loss. Compared with 

 the calf, its individual value is much greater. 



Therefore, when abortion becomes widespread in a region 

 where horse breeding is very extensive and where the animals 

 have a high value, the losses are enormous and it is difficult to 

 state, without reliable statistics, in which species of animal 

 abortion causes the greatest monetary losses, although we must 

 admit that the economic loss from abortion in cows has received 

 more attention and is more apparent. The view is doubtless 

 correct that abortion in cows is more widespread, largely owing 

 to the fact that the infection apparently has a better opportunity 

 for spreading. The disease in cows also has better opportunity 

 for perpetuation owing to the fact that cows are bred through- 

 out the entire year, whereas, in the mare, the breeding is more 

 concentrated at one season, and an outbreak of abortion may 

 vent its full force by destroying all the fetuses in a stable and 

 then cease to exist for want of material to sustain it. 



Most authors consider infectious abortion as a universal mal- 

 ady which may be transferred from one species of animal to an- 

 other. A few cases have been cited, in our literature, where in- 

 fectious abortion has prevailed simultaneously on the same farm 

 among cows and mares, but this is a very rare occurrence and 

 quite contrary to the rule. Infectious abortion occurring in dif- 

 ferent species of animals simultaneously upon the same farm is 

 no more frequent, than should be expected as a coincidence. 

 There is no reason why infectious abortion of mares and cows 

 may not co-exist as two distinct affections on one farm. In our 

 earlier experience, we observed chiefly infectious abortion of the 

 mare and, in our territory, the different species of pregnant ani- 

 mals largely occupied the same enclosures. 



The abortions in the mare, in our experience, very largely 

 occurred in the open pasture or field. Though there were habit- 



